Abstract: A solid crystalline material of formula (I): LiaMY4XZ: wherein: a is from 5 to 8: M is selected from Si, Al, Sb, Sn, B, Ga and Ge, a mixture thereof, or a mixture thereof comprising P1-xM? wherein M? is selected from Si, Al, Sb, Sn, B, Ga and Ge or a mixture thereof and wherein 0<x?1; wherein when M is Si at least one of X and Z is O; Y is O1-bSb, wherein b is from 0 to 0.5; and X and Z are each independently selected from O, S, F, Cl, Br, I or a mixture thereof. The solid crystalline material suitably provides a solid ionic conductor for use in a solid-state battery. A solid crystalline material comprising a solid solution, a solid-state battery comprising the solid crystalline material and a method of preparing the solid crystalline are also disclosed.

Abstract: A solid crystalline material of formula (I): AzDY4Xx, wherein each A is independently selected from Li, Na, K and Mg; D is selected from Si, Al, P, B, Ga, Ge, S, Mo, W, V, Sn, Sb, Nb and Ta, or a mixture thereof; each Y is independently selected from O, S, F, Cl, Br or a mixture thereof; each X is independently selected from F, Cl, Br, I, O, S, BH4 or a mixture thereof; z is from 2 to 8; and x is from 1 to 3. The solid crystalline material suitably provides a solid ionic conductor for use in a solid-state battery. A mixed solid crystalline material comprising the solid crystalline material, a solid-state battery comprising the solid crystalline material and a method of preparing the solid crystalline are also disclosed.